First Look: Citrix XenServer 4.1 Beta

In rolling out its latest virtualization solutions, including XenServer 4.1, Citrix is stepping deeper into an increasingly crowded IT segment that includes heavyweights like VMware and Microsoft -- the latter which is now beta testing its Hyper-V virtualization product.

But don't be mistaken: comparing Hyper-V's virtualization to XenServer's approach is like comparing Hotmail to Exchange. They both provide the same, basic service but with significantly different levels of functionality. Think of Hyper-V as most likely to be favored by strictly Windows shops; and enterprises that seek out a virtualization solution integrated tightly with Windows. XenServer might be a solution for those who want their virtualization on an independent platform, able to support a variety of guest hosts, be it Windows, or the various flavors of Linux.

Both Hyper-V and XenServer 4.1 are in beta. The CMP Channel Test Center has been taking a look at both products to examine basic features and functionality of each. Keeping in mind both have different aims in the data center, here's how they each looked in the testing environment:

The Install Process-- Both products are easy to install, with Windows' familiar wizard style of UI giving Hyper-V a slight user-friendly edge. Installation was carried out on a low-end server: a Dell Power Edge T105 with dual-core 1.80 GHz AMD Opteron processor, 1 GB memory and 74 GB HDD. A right-click on "Add Role" under "Roles" in Server Manager and the Hyper-V install was underway. A restart is required, but the install took about 5 minutes. XenServer was installed off a bootable disk onto a bare metal server -- a Gateway E9425R quad-core 1.86 GHz Xeon processor with 1GB memory and 60 GB HDD. The install process loads a LINUX kernel that gives the option of installing the XenServer host, load a driver, or if an existing OS is installed, converting that OS to a virtual machine (physical to virtual, or P2V). Installation was about 10 minutes.

Virtual Machine Creation and Management-- The Test Center then compared creation of VMs. The Hyper-V's management console is inside Server Manager and easy to navigate once again via the Windows interface familiarity. Setup prompts for virtual memory and disk space allocation. During setup of a Windows 2003 VM, Test Center engineers were able to allocate virtual disk space that exceeded the physical disk size. There were no warnings given regarding size limitation, and the install proceeded. Install of 2003 VM took 37 minutes. As the Test Center reported in an earlier review, the problem of the virtual network adapter binding to the physical network adapter showed up in this test as well.

Installation of the Integrated Service setup installed the virtual adapter, and the installation was a snap. XenServer's management console is through its client, XenCenter. For testing, XenCenter was installed on the same Server 2008 box that Hyper-V was loaded on. Both products played nicely with one another, no crashes or error messages even with Hyper-V services and XenCenter running concurrently. Another Windows 2003 VM was created using XenCenter.

XenCenter employs the use of templates to create virtual instances of Server 2000, 2003, 2003 x64, XP SP2 or "other install media" (the installation CD for the OS is still required, however). The templates provide preloaded configuration, making for a more expedient server setup. Setup prompts for memory allocation, disk size and number of CPUs to allocate. There were no issues with the virtual network adapter installing properly. XenServer was tested to see if it would allow the creation of a virtual disk that was larger in size than the physical disk.

It seemed to let the user allocate a size that exceeded the physical drive without any warnings -- but the system quietly reset the drive space to the maximum size the physical drive allowed. Seamless idiot-proofing. Installation of 2003 VM took 31 minutes.

Inside the VMs-- Each platform allows the creation of "virtual" servers inside another operating environment. Inside virtual machines on each platform, there are similarities and differences that are worth noting.

Hyper-V and XenServer offer reduced and full-screen views. Keyboard and mouse input in Hyper-V required pressing CNTRL-ALT-Left Arrow (a default sequence that the user can change) to switch control back and forth between the VM and the local environment, which becomes a bit tiresome after awhile. In XenCenter, switching control between virtual and local environments is done without any user intervention. File copying was comparable for both. On each platform, within a Windows Server 2003 virtual machine, a 1.5 GB file took slightly more than a minute to copy from a share to the desktop. Applications open in the VMs without any latency.

Logical grouping of VMs is only evident in XenServer. From XenCenter, "pools" of virtual servers can be created. In the Hyper-V console, there is a tree hierarchy, with the physical server at the top-most level and the virtual machines directly under at the same level.

Taking a snapshot in Hyper-V was a simple mouse click. Reverting to the snapshot image was just as fundamental, the VM restarted automatically booting back up with the message, "revert succeeded." However there were no readily accessible log file that detailed the snapshot creation and reversion. Hyper-V events are written to the Event Viewer in a mass of sub folders. It was hard to tell which one, if any contained logging about the snapshot events.

There were no menu items that readily allowed us to create a snapshot in XenServer.

It will be interesting to see each of these products in final release. With the virtualization market in heated competition, the collaborative efforts of Citrix and Microsoft should make for the race to be top of the virtual mountain even more interesting.